1. Field of the Invention
The present invention relates to a plasma processing apparatus employing the radio frequency induction method.
2. Description of the Related Art
Conventionally, as an apparatus in which, e.g., a semiconductor wafer is placed in a processing chamber to perform a plasma process, a parallel plate type plasma processing apparatus using a radio frequency (radio frequency) is widely employed. A reactive ion etching apparatus (RIE) in which two parallel plate electrodes are arranged in a processing chamber is exemplified as this kind of apparatus. A radio frequency wave is applied to one or both of the electrodes to generate a plasma between the two electrodes. The flow of the plasma is incident on the target surface of an object to be processed by a self-bias potential difference between the plasma and the object to be processed, thereby performing an etching process.
In the conventional plasma processing apparatus such as the above parallel plate type plasma processing apparatus, however, micropatterning in units of submicrons and further in units of sub-half microns which are required with high integration of a semiconductor wafer is difficult to perform. In order to perform this process using a plasma processing apparatus, it is important to control a high-density plasma with a high precision in a low-pressure atmosphere. In addition, a highly uniform plasma is required so as to correspond to a wafer having a large diameter. In a plasma processing apparatus using an electrode, the electrode itself becomes a source of heavy-metal contamination in generation of a plasma. In particular, this becomes typical when micropatterning is required.
In order to establish a new plasma source in accordance with such a technical requirement, many approaches have been made from various viewpoints. For example, a radio frequency-induced plasma generating apparatus using a radio frequency antenna is disclosed in European Pat. Appln KOKAI Publication No. 379,828. In this radio frequency induced plasma generating apparatus, one surface of a processing chamber opposing a wafer rest table consists of an insulator, e.g., quartz glass, and a radio frequency antenna constituted by, e.g., a spiral coil is mounted on the outer wall surface of the processing chamber. A radio frequency power is applied to the radio frequency antenna to form a radio frequency electromagnetic field in the processing chamber. The electrons flowing in the electromagnetic field space are caused to collide against neutral particles in the process gas, and to ionize the gas, thereby generating a plasma.
When the plasma process is performed using the above plasma processing apparatus using the radio frequency induction method, the density of a plasma induced in the chamber tends to be non-uniform particularly in the radial direction. Further, when the plasma process with a very high precision is to be performed in units of sub-half microns which are popular today, a uniform, high-density plasma having good reproducibility is required to be generated in a chamber. Therefore, a technique for controlling the density of a plasma in the chamber with a high precision must be urgently established.